Technical Field
The present disclosure relates to a fingerprint identification apparatus and method, in particular, to a fingerprint identification apparatus and method capable of simultaneously identifying fingerprint image and oxygen saturation.
Description of Related Art
The so-called fingerprint recognition/identification as the name suggests is the use of unique fingerprint identification information on the human finger. One typical fingerprint identification apparatus may feature two elements, one of which is fingerprint sensor to collect a complete fingerprint image and the other is fingerprint algorithm. When the original fingerprint image is captured by the fingerprint sensor, the captured will be processed by the fingerprint algorithm including the extraction of fingerprint features to generate a fingerprint template before having the original fingerprint image discarded. With the fingerprint template, fingerprint comparison could be performed.
Traditionally, capacitive fingerprint sensor and optical fingerprint sensor could be used. Among the capacitive fingerprint sensors, RF capacitive sensing, pressure sensing, and thermal sensing are widely employed. The capacitive fingerprint sensor could have miniaturized sensors such as densely disposed pressure sensors or capacitance sensors integrated within a chip. When the surface of the chip is pressed by the finger, the internal micro capacitance sensors depending on different amount of charges or difference in temperature because of the aggregation of fingerprint valleys or ridges could forming the fingerprint image.
Despite the capacitive sensors are compact in size and therefore suitable to be incorporated into one portable device, manufacturing cost and durability could be disadvantages to be taken into account. Specifically, for the capacitive sensors to maintain their size (surface) for the press of the finger, certain area of the whole wafer may be cut, increasing the manufacturing cost of the capacitive sensors. Furthermore, due to the capacitive sensors could be uncapped semiconductor chips environmental factors such as sweat could damage the sensors and the capacitive sensors are prone to static charges, seriously undermining durability of such sensors and shortening operational life of the same. To minimize the impact associated with the environmental factors, certain capacitive sensors could have a layer of sapphire substrates attached to their surface for protection, undoubtedly increasing the cost in manufacturing.
Optical sensors, meanwhile, as the most primitive option to capture the fingerprint, include a light source, a dispersive prism, and a charge-coupled device (CCD). When the finger presses the dispersive prism, the fingerprint image could be obtained based on the absorption and even destruction of the total reflection by the fingerprint valleys and the fingerprint ridges. The fingerprint image could be extracted and outputted by CCD. At the time of the capture of the fingerprint, the finger is pressed upon optical elements such as acrylic or glass rather than the chip having the sensor itself. Thus, the optical sensors could be relatively inexpensive and durable. But the optical sensors are disadvantageous in its size and the complexity of assembly, rendering difficult for such sensors to be used within the portable device.
In addition, some perpetrators have used fake finger in silicone trying to get around the identification process. Such fake fingers could virtually emulate the real fingers with fingerprint and capillaries. Therefore, with the fake fingers to press the conventional fingerprint identification devices the characteristics created by the silicone such as the deformation and the fingerprint could be indistinguishable from the viewpoint of the traditional devices, resulting in the loophole in identification.
Therefore, the present disclosure could be solving the problems associated with the conventional capacitive fingerprint sensors and the optical sensors.